A systematic review of substance use and substance use disorder research in Kenya

Objectives The burden of substance use in Kenya is significant. The objective of this study was to systematically summarize existing literature on substance use in Kenya, identify research gaps, and provide directions for future research. Methods This systematic review was conducted in line with the PRISMA guidelines. We conducted a search of 5 bibliographic databases (PubMed, PsychINFO, Web of Science, Cumulative Index of Nursing and Allied Professionals (CINAHL) and Cochrane Library) from inception until 20 August 2020. In addition, we searched all the volumes of the official journal of the National Authority for the Campaign Against Alcohol & Drug Abuse (the African Journal of Alcohol and Drug Abuse). The results of eligible studies have been summarized descriptively and organized by three broad categories including: studies evaluating the epidemiology of substance use, studies evaluating interventions and programs, and qualitative studies exploring various themes on substance use other than interventions. The quality of the included studies was assessed with the Quality Assessment Tool for Studies with Diverse Designs. Results Of the 185 studies that were eligible for inclusion, 144 investigated the epidemiology of substance use, 23 qualitatively explored various substance use related themes, and 18 evaluated substance use interventions and programs. Key evidence gaps emerged. Few studies had explored the epidemiology of hallucinogen, prescription medication, ecstasy, injecting drug use, and emerging substance use. Vulnerable populations such as pregnant women, and persons with physical disability had been under-represented within the epidemiological and qualitative work. No intervention study had been conducted among children and adolescents. Most interventions had focused on alcohol to the exclusion of other prevalent substances such as tobacco and cannabis. Little had been done to evaluate digital and population-level interventions. Conclusion The results of this systematic review provide important directions for future substance use research in Kenya. Systematic review registration PROSPERO: CRD42020203717.


Search strategy
A search was carried out in ve electronic databases: PubMed, PsychINFO, Web of Science, Cumulative Index of Nursing and Allied Professionals (CINAHL) and Cochrane Library. The full search strategy can be found in Additional le 2 and takes the following form: (terms for substance use) and (terms for substance use outcomes of interest) and (terms for region). The searches spanned the period from inception to date. No lter was applied. A manual search was done in Volumes 1, 2 and 3 (all published volumes by the time of the search) of the recently launched AJADA journal from the NACADA website and additional articles identi ed (12,16,17).

Study selection
Following the initial search, all articles were loaded onto Rayyan, a soft-ware for screening and selecting studies during the conduct of systematic reviews (18), and checked for duplicates. After duplicate removal, the abstract and titles of retrieved articles were independently screened by two authors based on a set of pre-determined eligibility criteria. A second screening of full text articles was also done independently by two authors and resulted in an 88.7% agreement. Disagreements during each stage of the screening were resolved through discussion and consensus.

Inclusion criteria
Since we sought to map existing literature on the subject, our inclusion criteria were broad. We included all studies on substance use if (i) the sample or part of the sample was from Kenya, (ii) they were original research articles, (iii) they had a substance use exposure, (iv) they had a substance use/SUD related outcome such as prevalence, pattern of use, prevention and treatment, and (iv) they were published in English or had an English translation available. We included studies conducted among all age groups and studies that used all designs both quantitative and qualitative.

Exclusion criteria
Studies were excluded if: (i) they were cross-national and did not report country speci c results (ii) they did not report substance use as an exposure, and did not have substance use related outcomes or as part of the outcomes, (iii) they were review articles, dissertations, conference presentations/abstracts, commentaries or editorials, (iv) and the full text articles were not available.

Data extraction and synthesis
We prepared 3 data extraction forms based on three categories of studies i.e.: 1. Studies reporting on the epidemiology of substance use/SUD 2. Studies evaluating substance use/SUD interventions and programs 3. Studies qualitatively exploring various themes on substance use/SUD (but not assessing interventions) The forms were piloted by F.J. and S.K. and adjustments made to the content. Data extraction was then done using the nal form by all authors and double checked by F.J. for completeness and accuracy. Discrepancies were resolved by discussion with S.K. and E.T. until consensus was achieved. The following data was extracted for each study category: 1. Studies reporting on the epidemiology of substance use/SUD: study design, study population characteristics, study setting, sample size, age and gender distribution, substance(s) assessed, standardized tool/criteria used, main ndings (prevalence, risk factors, other key ndings).
2. Studies evaluating substance use/SUD interventions and programs: study design, study objective, sample size, name of the intervention/program, person delivering intervention, outcomes and measures, and main ndings 3. Studies qualitatively exploring various aspects of substance use/SUD other than programs and interventions: study objective, methods of data collection, study setting, study population, age and gender distribution, and main ndings The results have been summarized descriptively and organized by the three categories above.
Quality assessment of the studies Quality assessment was conducted by S.K. using the Quality Assessment Tool for Studies with Diverse Designs (QATSDD) (19). F.J. & J.B. double checked the scores for completeness and accuracy. Any disagreements were discussed and resolved by consensus. We had initially planned to use the National struggling with alcohol use and alcohol being brewed in the home (67). Alcohol use was linked to various health factors including glucose intolerance (68); poor cardiovascular risk factor control (69), having a diabetes mellitus diagnosis (70), hypertension (65,71), default from tuberculosis (TB) treatment (72), depression (49), psychological Intimate Partner Violence (IPV) (73), physical and sexual violence (74), tobacco use (66,73), and increased risk laryngeal (75) and esophageal cancer (76,77). Finally alcohol use was associated with involvement in Road Tra c Accidents (RTAs) (78,79), having injuries (78,80,81), and with having concurrent sexual relationships (66).
Other topics explored:In addition to prevalence and associated factors, these studies explored other topics including agreement between self-reported alcohol use and the biomarker phosphatidyl ethanol (92), primary health care workers self-e cacy for SUD management (93), reasons for substance use (27,30,94,95), and tobacco quit intentions(96). Papas et al. (92) reported a lack of agreement between self-reported alcohol use and the biomarker phosphatidyl ethanol among PLHIV with AUD. Among primary health care workers, self-e cacy for SUD management was lower in those practicing in public facilities and perceiving a need for AUD training. In that study, higher self-e cacy correlated with a higher proportion of patients with AUD in one's setting, access to mental health worker support, HCW's cannabis use at a moderate risk level, and belief that AUD is manageable in outpatient settings. Common reasons for substance use included leisure, stress and peer pressure among psychiatric in-patients (30), curiosity, fun, and peer in uence among college students (94); peer in uence, idleness, easy access, and curiosity among adults in the community (27); and peer pressure, to get drunk, to feel better and to feel warm among street children (95 intentions for tobacco use and reported that 28% had tried to quit in past 12 months; 60.9% had never tried to quit, only 13.8% had ever heard of smoking cessation medication. Intention to quit smoking was associated with being younger, having tried to quit previously, perceiving that quitting smoking was bene cial to health, worrying about future health consequences of smoking, and being low in nicotine dependence. A complete description of the prevalence studies has been provided in additional le 3.

Studies evaluating substance use/ SUD programs and interventions
A total of eighteen studies evaluated speci c interventions or programs for the treatment and prevention of substance use (see Additional le 4). These were carried out between 2009 and 2020. The studies used various approaches including randomized control trials (RCT) (99-105) mixed methods (106-108), non-concurrent multiple baseline design (109), quasi experimental (110), cross-sectional (111,112), and qualitative (113)(114)(115). One study employed a combination of qualitative methods and mathematical modeling (116).
The interventions were delivered using various approaches including trained lay providers (101,106,109,110), digital health means (99), and trained primary care workers such as nurses (100,102), and VCT service providers (Mackenzie 2009 (103), while another the use of multiple substances (105). All interventions had a positive impact on substance use except the study that used the contingency management approach (104). The interventions were delivered in various settings as follows: community settings (n=6) (99,(102)(103)(104)109,110) of which one was delivered in a HIV prevention drop in center (102), HIV treatment or testing out-patient clinics (n=3) (101,106,107), alcohol and drug abuse rehabilitation facility (n=1) (100), and within a college (n=1) (105). One study described the process of culturally adapting a CBT intervention for alcohol use, for use among a population of PLHIV (106).
Five studies evaluated various aspects of substance use treatment programs. The studies evaluated perceptions on bene ts of methadone programs (113,116) and NSPs (115), healthcare workers knowledge and practices on tobacco cessation (112), and utilization of community based outpatient SUD treatment services (111). The methadone and NSP programs were perceived as bene cial and impactful by stakeholders and service users (113,115) and knowledge and practice on tobacco cessation as inadequate (112). Deveau et al., 2010 (111) reported a 42% abstinence rate 0-36 months post-treatment termination.
Two studies evaluated population-level interventions. One evaluated the appropriateness and effectiveness of HIC anti-tobacco adverts in the African context and found the adverts to be effective and appropriate (108). Another study that examined community member's perspectives on the impact of the government's public education messages on alcohol abuse reported the messages as ineffective and unpersuasive (114). A complete description of included intervention studies is in additional le 4.
Various themes were explored in these qualitative studies including risk and protective factors for substance use (120,127,131,134), health and or socioeconomic effects of substance use (119,122,123,130,132), perceptions on heroin use (133), transitions from heroin smoking to injection (117), and stages of change in participants enrolled in an intervention (121). Substance use was perceived as having a negative socio-economic and health impact (122,132). Speci cally, substance use was perceived to have a negative impact on contraceptive use (128), on utilization of antenatal and maternal & child health services (137), as well as on sexual and reproductive health (130). In addition, substance use emerged as a driver of risky sexual behavior and HIV among both adults (118,138) and adolescents (120,134). Several factors were perceived to contribute to substance use including gender inequality, in uence of intimate partners and the need to cope with stress among women (119,124,125), and stigma and perceived medicinal value among PLHIV (135). Finally, access to care for substance use was reported as limited (119,132,135).

Discussion:
This is to our knowledge, the rst study to summarize empirical work done on substance use and SUDs in Kenya. More than a half (77.8%) of the reviewed studies investigated the area of prevalence and risk factors. Less common were qualitative studies exploring various themes (12.4%) and studies evaluating interventions and programs (9.7%). The rst study was conducted in 1982 and since then the number of publications has gradually risen. Most of the research papers (92.4%) were of moderate to high quality. The review nds that comparatively a lot of research work has been done on substance use in Kenya in relation to other Sub-Saharan African (SSA) countries, with 185 papers published by the time of the search. Two recent scoping reviews, reported that only 53 and 7 papers focusing on substance use had been published in South Africa (between 1971 and 2017) (9) and in Botswana (between 1983 and 2020) respectively (8).

Epidemiology of substance use/SUD
Studies assessing prevalence, patterns and risk factors dominated the literature. The studies were conducted across a broad range of study settings and populations. In addition, a wide range of important health and socio-demographic factors were examined for their association with substance use. Most studies had robust sample sizes and were conducted using diverse designs including cross-sectional, case-control and cohort. The studies showed a signi cant burden of substance use among both adults and children and adolescents. In addition substance use increased the odds of negative mental and physical health outcomes consistent with ndings documented in global reports (2,3). These ndings highlight the importance of making the treatment and prevention of substance use and SUDs of high priority in Kenya.
Key evidence gaps were identi ed within this category: 1. The prevalence and risk factors for substance use among certain vulnerable populations for whom substance use can have severe negative consequences, had not been investigated. For example, no study had included police o cers or persons with physical disability, only one study had its participants as pregnant women (38), and only 2 studies had been conducted among HCWs (93, 139).
2. The prevalence of emerging substances was investigated by only one study (140). These substances are increasingly becoming a public health threat globally (141) yet their use remains poorly documented in Kenya

Interventions and programs
Given the signi cant documented burden of substance use and SUDs in Kenya, it was surprising that few studies had focused on developing and testing treatment and prevention interventions for substance use. A possible reason for this is limited expertise in the area of intervention development and testing. For example, research capacity in implementation science has been shown to be limited in resource-poor settings such as ours (142).
Of note is that most of the tested interventions had been delivered by lay providers (101,106,109) and primary care workers (100, 102, 107) indicating a recognition of task-shifting as a strategy for lling the mental health human resource gap in Kenya.
Overall, study ndings indicated feasibility and bene t for the programs and interventions evaluated except for one study which showed no effect for a contingency management type intervention (104). Several research gaps were identi ed within this category.
1. Out of the 11 individual-level interventions tested, all targeted alcohol use except one which focused on khat (103) and another that targeted several substances (105). No individual-level interventions targeted tobacco and cannabis use despite the two being the second and third most commonly used substances in Kenya (6). (108, 114). Several cost-effective population-level interventions have been recommended by WHO e.g. mass media education and national toll free quit line services for tobacco use, and brief interventions integrated into all levels of primary care for harmful alcohol use (143). Such strategies need to be tested for scaling up in Kenya.

Few studies had evaluated the impact of population-level interventions
3. None of the interventions had been tested among important vulnerable populations for whom local research already shows a signi cant burden e.g. children and adolescents, the Lesbian Gay Bisexual Transgender & Queer (LGBTQ) community, HCWs, prisoners, and refugees and IDPs. In addition, no interventions had been tested for police o cers and pregnant women, and no studies had evaluated interventions to curb workplace substance use.
4. Only one study evaluated digital strategies for delivering substance use interventions (99) yet the feasibility of such strategies has been demonstrated for other mental disorders in Kenya (144). Moreover, the time is ripe for adopting such an approach to substance use treatment given the fact that the country currently has a mobile subscriptions penetration of greater than 90% (145).

5.
No studies had evaluated the impact of other interventions such as mindfulness and physical exercise. Meta-analytic evidence suggests that such strategies hold promise for reducing the frequency and severity of substance use and craving (146, 147).

Qualitative studies
The qualitative studies provided in-depth understanding of the factors contributing to, and the socio-economic and health impact of substance use among both adults and adolescents. Most of the work however focused on PWID use and FSWs. Future qualitative work should focus on examining the drivers and impact of substance use in several other populations for example persons with other mental disorders, persons with physical disabilities, police o cers, and persons using other substances such as tobacco and cannabis.

Limitations
The aim of this systematic review was to provide an overview of the existing literature on substance use and SUD research in Kenya, we therefore did not undertake a meta-analysis and detailed synthesis of the ndings of studies included in this review. In addition, variability in measurements of substance use outcomes precluded ability to summarize the study ndings. For quality assessment, detailed assessments using design speci c tools were not possible given the diverse methodological approaches utilized in the studies. We therefore used a single tool for the quality assessment of all studies. The results of the quality assessment are therefore to be interpreted with caution. Nonetheless this review describes for the rst time the breadth of existing literature on substance use and SUDs in Kenya, identi es research gaps and provides important directions for future research.

Conclusion:
The purpose of this systematic review was to map the research that has been undertaken on substance use and SUDs in Kenya. Epidemiological studies dominated the literature and indicated a signi cant burden of substance use among both adults and adolescents. Our ndings indicate that there is a dearth of literature regarding interventions for substance use and we are calling for further research in this area. Speci cally, interventions ought to be tested not just for alcohol but for other substances as well, and among important at risk populations. In addition, future research ought to explore the feasibility of delivering substance use interventions using digital means, and the bene t of other interventions such as mindfulness and physical exercise. Future qualitative work should aim at providing in-depth perspectives on substance use among a populations excluded from existing literature e.g. police o cers, persons using other substances such as tobacco and cannabis and persons with physical disability. Availability of data and materials All data generated or analyzed during this study are included in this published article [and its supplementary information les].

Competing interests
The authors declare that they have no competing interests.

Funding
There are no sources of funding to declare Authors' contributions F.J. and S.K. developed the protocol for the systematic review. S.K. searched the databases. S.K. and F.J. conducted the screening and selection of studies. All authors contributed to data extraction. Quality assessment was done by S.K., F.J. and J.B. All authors contributed to report writing. All authors read and approved the nal manuscript.  Line graph showing the trends in publications on substance use/SUD in Kenya since inception